Every tool has its own algorithm.
Godaddy appraisal counts from simillar domain name sale history
Estibot from keyword search in Google
Nameworth and Nocta Domain counts from other algorithm
There are some domain appraisals count from...
Always use escrow for selling and buying above 100$.
If you are paid by Paypal, buyer can charged back after you sent the domains.
Don't use bitcoin or crypto for buying domains, after you transfer the money, you can be cheated not getting the...